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We describe an experiment in which Bose-Einstein condensates and cold atom clouds are held by a microscopic magnetic trap near a room-temperature metal wire 500 microm in diameter. The lifetime for atoms to remain in the microtrap is measured over a range of distances down to 27 microm from the surface of the metal. We observe the loss of atoms from the microtrap due to spin flips. These are induced by radio-frequency thermal fluctuations of the magnetic field near the surface, as predicted but not previously observed.

This article raises questions about what the word 'knowledge' refers to. Drawn from some 40 years of collaborative work on knowledge democracy, the authors suggest that higher education institutions today are working with a very small part of the extensive and diverse knowledge systems in the world. Following from de Sousa Santos, they illustrate how Western knowledge has been engaged in epistemicide, or the killing of other knowledge systems. Community-based participatory research is about knowledge as an action strategy for change and about the rendering visible of the excluded knowledges of our remarkable planet. Knowledge stories, theoretical dimensions of knowledge democracy and the evolution of community-based participatory research partnerships are highlighted.

We use collective oscillations of a two-component Bose-Einstein condensate (2CBEC) of 87 Rb atoms prepared in the internal states |1 ≡ |F = 1, mF = −1 and |2 ≡ |F = 2, mF = 1 for the precision measurement of the interspecies scattering length a12 with a relative uncertainty of 1.6 × 10 −4 . We show that in a cigar-shaped trap the three-dimensional (3D) dynamics of a component with a small relative population can be conveniently described by a one-dimensional (1D) Schrödinger equation for an effective harmonic oscillator. The frequency of the collective oscillations is defined by the axial trap frequency and the ratio a12/a11, where a11 is the intraspecies scattering length of a highly populated component 1, and is largely decoupled from the scattering length a22, the total atom number and loss terms. By fitting numerical simulations of the coupled Gross-Pitaevskii equations to the recorded temporal evolution of the axial width we obtain the value a12 = 98.006(16) a0, where a0 is the Bohr radius. Our reported value is in a reasonable agreement with the theoretical prediction a12 = 98.13(10) a0 but deviates significantly from the previously measured value a12 = 97.66 a0 [1] which is commonly used in the characterisation of spin dynamics in degenerate 87 Rb atoms. Using Ramsey interferometry of the 2CBEC we measure the scattering length a22 = 95.44(7) a0 which also deviates from the previously reported value a22 = 95.0 a0 [1]. We characterise two-body losses for the component 2 and obtain the loss coefficients γ12 = 1.51(18) × 10 −14 cm 3 /s and γ22 = 8.1(3) × 10 −14 cm 3 /s.

We observe the coherence of an interacting two-component Bose-Einstein condensate (BEC) surviving for seconds in a trapped Ramsey interferometer. Mean-field driven collective oscillations of two components lead to periodic dephasing and rephasing of condensate wave functions with a slow decay of the interference fringe visibility. We apply spin echo synchronous with the self-rephasing of the condensate to reduce the influence of state-dependent atom losses, significantly enhancing the visibility up to 0.75 at the evolution time of 1.5 s. Mean-field theory consistently predicts higher visibility than experimentally observed values. We quantify the effects of classical and quantum noise and infer a coherence time of 2.8 s for a trapped condensate of 5.5 × 10 4 interacting atoms.

We investigate the spatially dependent relative phase evolution of an elongated two-component Bose-Einstein condensate. The pseudospin-1 2 system is comprised of the |F = 1, mF = −1 and |F = 2, mF = +1 hyperfine ground states of 87 Rb , which we magnetically trap and interrogate with radio-frequency and microwave fields. We probe the relative phase evolution with Ramsey interferometry and observe a temporal decay of the interferometric contrast well described by a mean-field formalism. Inhomogeneity of the collective relative phase dominates the loss of interferometric contrast, rather than decoherence or phase diffusion. We demonstrate a technique to simultaneously image each state, yielding subpercent variations in the measured relative number while preserving the spatial mode of each component. In addition, we propose a spatially sensitive interferometric technique to image the relative phase.

We report on the adiabatic splitting of a Bose-Einstein condensate of 87Rb atoms by an asymmetric double-well potential located above the edge of a perpendicularly magnetized TbGdFeCo film atom chip. By controlling the barrier height and double-well asymmetry, the sensitivity of the axial splitting process is investigated through observation of the fractional atom distribution between the left and right wells. This process constitutes a novel sensor for which we infer a single shot sensitivity to gravity fields of deltag/g approximately 2 x 10(-4). From a simple analytic model, we propose improvements to chip-based gravity detectors using this demonstrated methodology.

Abstract. A microscopic Ioffe-Pritchard trap is formed using a straight, currentcarrying wire, together with suitable auxiliary magnetic fields. By measuring the distribution of cold rubidium atoms held in this trap, we detect a weak magnetic field component ∆B z parallel to the wire. This field is proportional to the current in the wire and is approximately periodic along the wire with period λ = 230 µm. We find that the decrease of this field with distance from the centre of the wire is well described by the Bessel function K 1 (2πy/λ), as one would expect for the far field of a transversely oscillating current within the wire.